Oxidation of hydrocarbons



Oct. 27, 1942. .1. E. BLUDwoRTH OXIDATION OF HYDROCARBONS Filed May 28, 1940 Ll .5.68 Al w/ A REYs Patented Oct. 27, 1942 oma'noiv or maconnerie Joseph E. Blndworth, Cumberland, Md., assigner to Celan ration of Delaware ese Corporation ot America, a corpol Application May 28, 1940, Serial )10.337593 (Cl. 26H51) Claims.

This invention relates to the partial oxidation of hydrocarbons, such as mineral oil, natural gas,

coal and coal derivatives, to obtain oxides, aldel hydes, alcohols, acids, etc.

An object of the invention is the economic recovery ofthe products formed in the partial oxidation of hydrocarbons. Another object of the invention is the recovery of water-soluble acids formed by the partial oxidation oi hydrocarbons.

Other objects oi the invention will appear i'rom the following description and drawing.

Hydrocarbons, such as butane for example. may

be partially oxidized by reacting at elevated temperature the hydrocarbon with oxygen'in the presence of a diluent, preferably steam, and then stopping the reaction at the desired degree of oxidation by quenching with water. This process is more fully described in my U. S. Patent No. 2,128,909 of September 6, 1938. The resulting products, with the exception of the water-soluble acids, may be ilashed from this quenching water, the water-soluble acids being separated from the water by' solvent extraction or by conversion of the same into a salt such as calcium acetate in the case of acetic acid. The amount of acid in the water may be from a trace (01%) to 3% or 4% by weight depending upon conditions employed in the oxidation process.` Under the preferred condition of oxidation to produce the highest yield of acetone and acetaldehyde,.

there is about 0.07% by weight oi acid in the quench water. Due to the large amount or water required to be distilled olf, the recovery of this small amount of acid is uneconomical, yet in a large plant the total amount of acid used is very great. For instance, for every 10 tons of butane oxidized there may be produced 250,000 gallons of water containing about 0.07% by weight of acid. In prior methods this water was discharged from the plant as its corrosive nature prevented its use.

I have now found that by using this water again in, the quench the acid content thereof may be built up to from 1 to 5% by weight making the recovery of the acid by solvent extraction or conversion into salts economical. 'I'his operation not only recovers the acid but also reduces the amount or fresh water required since the water, after the substantial removal of' the acid, may be used again. By this new process the amount of fresh water required for every 10 tons oi butane oxidized may be reduced from 250,000 gallons to about 26,000 gallons. The reduction in the amount oi.' water required to be puriiled vmuy 10st :muy mcreasesvthe prent derived from theoxidation process. The apparatus required for my new process is substantially the same as i'or my prior process described in Patent No. 2,128,909,` since, although the quench water of my new process is corrosive and hot, it traverses only that part oi the plant originally constructed to withstand the corrosive action of the more dilute acid, namely the quench chamber and the subsequent piping.

In accordance with my invention, I partially oxidize a hydrocarbon or mixture or hydrocarbons by reacting the same at an elevated temperature and pressure with oxygen or an oxygen bearing compound in the presence of a diluent and then quenching the reaction mixture with water to stop the oxidation at the required degree .of oxidation. 'I'he unreactedhydrocarbon and acid -which is returned to quench the oncoming reaction mixtures until the acid concentration in the water is such as to warrant economical removal. The acid may then be concentrated by solvent, extraction or by precipitation as a `salt of the acid and the steam or water returned to the system.

This invention is applicable to the partial oxidation of any suitable hydrocarbon, such as a parailln base or asphalt base'mineral oil, natural gas, coal or coal derivatives, and hydrocarbons alreadyv containing oxygen atoms such as alcohols, ketones and aldehydes. It is of particular importance, however. to the partial oxidation of hydrocarbons, vsuch as butane, isobutane, propane, pentane, light petroleum distillates and similar'hydrocarbons containing from 3 to 20 carbon atoms to produce acetone, acetaldehyde and/or lower monohydric alcohols. It is also `within the scope of this invention to so regulate the reaction and to employ `various eatalysts such that there is produced unsaturated compounds, cyclic ethers, such as tetramethylene be nitrogen. carbon dioxide or other relatively ingen supplying agent may be oxygen, air etc. The

temperature oi reaction may vary considerably, it being somewhat dependent upon pressure. Prefand the recovery of a large amountl of acid ior- 56 erably the reaction temperature is from 500 F.

1000 F. and the pressure from 150 pounds to 25 pounds per square inch during the reaction.

The process will now be described with reference to the accompanying drawing which shows diagrammatically a form of apparatus that may be used in carrying out the invention.

The hydrocarbon, diluent (preferably steam and recycle gas) and oxygen are either mixed and heated to reaction temperature or one or more of the constituents may be heated separately and then mixed together, as more fully described in my Patent No. 2.128.909. For instance, 1 part of butane and 8 parts of air which are heated to above 800 F. and 70 parts of steam. superheated at I and passed to a reaction chamber 2. 'I'he velocity of the mixed gases and the length of the reaction chamber 2 are so adjusted that the gases are maintained therein the desired length of time. proceed for a period of from 0.1 to4 3 seconds, preferably 0.3 to 0.5 second, To stop the reaction at the desired moment, the reaction gases and products are mixed with a relatively large amount of water. 'Ihe Clarge amount of water quenches the reaction by lowering the temperature of the reacting gases to below that at which oxidation products are formed. This quenching operation may be performed in quench chamber 3 by introducing the gases into a stream of Water flowing into said quench chamber.

The products of the reaction and the quenching liquid may then be passed by pipeline 4 through a cooler 4 into a hot accumulator 5 in which the volatile products, including the unreacted hydrocarbon, some acid aldehydes, etc., are flashed oir. 'I'he remainder of the products, such as the aldehydes, alcohols, acids, etc., remain in the liquid and are carried from the hot accumulator 5 by pipe 6 to a flash column 1. The gases separated from the liquid in the hot accumulator are carried by pipe 8 through a cooler 8 into a water absorber 9.

The single water absorber tower 9, which is preferably under pressure considerably above atmospheric, diagrammatically illustrated in the drawing is divided into an upper ten-tray section II and a lower three-tray section I2. It is to be understood, however, that the absorber arrangement may consist of two absorbers, one of ten trays and the other having three trays. All of Ordinarily the reaction is permitted to though the drawing shows that the water absorber has two sections, one of ten trays and one of three trays, obviously any two-stage arrangement for scrubbing the gases with water wherein the gases are first scrubbed by a limited quantity of water may be employed. The quantity of water should be as small as possible, i. e., only just suflicient to remove the acids from the gases coming from the hot accumulator.

The liquid coming from the hot accumulator 5 through pipe 6 and the liquid from the lower section I2 of the water absorber 9 through the pipe Il are introduced into the ash column 1 wherein the acetone, acetaldehyde, alcohols, etc. are ilashed from the liquid leaving only the acid. 'This acid containing liquid may then be led by a pipe I5 to a reboiler I Ii wherein the last traces of acetone and aldehydes are removed, while the water containing the acid is carried by pipe I'I to a condenser I8. From the condenser the water and acid may be carried by pipe I9 back to the l quench chamber 3. Some of the liquid coming the trays may be of the bubble cap type and may or may not be identical. The pipes from the tentray section are conducted outside the column at' I3 and do not empty into the lower three-tray section. The three trays in lower section I2 receive their scrubbing water from a, pump (not shown) delivering from a, source other than that delivering the water to the upper ten-tray section II and the lower section discharges through pipe I4 into the regular liquid coming from the quench and hot accumulator. The gases from the lower section I2 pass upward through bubble caps to the top ten-tray section II. The lower three-tray section uses only a small amount of water and it removes all of the entrained acid but only a small portion of the aldehydes. upper ten-tray section uses at least ten times more Water than the bottom three-tray section and it discharges into a separate column, a iiash column under substantially atmospheric Ipressure. which distills the aldehydes overhead yand discharges waste water coming from the trays. By this arrangement only the water from the lower three-tray section is used to dilute the acid in the liquid coming from the quench chamber 3. Al-

Thev

from the reboiler I6 may be withdrawn from the system at 2l to an evaporator or precipitator or other means of separating the acid from the water, the amount of liquid withdrawn being equal to the amount of water added to the system as synthesis steam, absorber water and the water of the reaction.

The quench water as used in the new arrangement is-corrosive and hot, but this does not produce any particular operating diilculties, since the quench chamber and subsequent piping are made of acid-resisting materials.

In prior methods the temperature of the reaction gases is reduced by pumping in cold water at the quench. Sufilcient cold water is added to reduce the reaction temperatures to approximately 328 F., where the process is being operated at pounds gauge pressure, which temperature is about 10 F. lower than the temperature of dry steam at 100 pounds pressure existing on the system at the quench point. In other words, cold water absorbs, as sensible heat, enough energy to cool the reaction gases to below reaction temperature without using any of its available latent heat. Since the ratio of latent heat to sensible heat is about 9 to 1, I have found that hot water would serve as well as cool quench water to produce a iinal quench temperature just above the temperature of saturated steam at the working pressure. I have also found that temperatures below 350 F. at 100 pounds gauge pressure are sufcient to quench the reaction. In employing hot water and 100 pounds working pressure the temperature of the reaction gases is reduced to about 338 F., i. e., the temperature oi saturated steam at 100 pounds pressure.

The quench water used in the new arrangement may be cool or have a temperature up to 205 F. where the quench water comes from the ila'sh column. If a hot water accumulator system is used, wherein no flashing occurs and instead a control cooler is used, temperatures as high as 300 F. to the quench are eective. 'I'he residual liquors that are to be used as quench recycle may be discharged from the reboiler to a flash column. These liquors contain acid, but no aldehydes or other volatile products. This fluid, as it leaves the reboiler, has a temperature of approximately 214 F. As the pressure is reduced between the accumulator and the iiash column from one or two pounds of pressure to atmospheric pressure a portion of the water flashes oli in the flash column. The temperature of the residue is thus reduced to some point lower than that of boiling water, i. e., to atemperature of 205 F. At this temperature ebullition has ceased, and the residue can be pumped l back to Athe quench zone. The flashing action vaporizes about 3% of the residue which maybe condensed and collected or passed out into the atmosphere. A certain proportion of the residue may be continuously or intermittently Withdrawn from the system to an acid concentrating process while a similar amount of liquid is added to the system. The added liquid may be fresh water or water containing acid. It is preferred to keep the concentration of acid in the water below 5%. However, higher concentrations may be employed. However, where the acid concentration is increased to above 1%, the recovery thereof is profitable.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. In the method of producing oxygenated organic compounds wherein hydrocarbons are subjcted in the vapor phase to oxidation in the presence of a diluent and the oxidation reaction products are quenched with aqueous liquid, the steps of returning a part of the aqueous liquid to the quenching zone, removing a part of the aque-v ous liquid and separating the acids therefrom.

2. In the method of producing oxygenated organic compounds wherein hydrocarbons are subjected in the vapor phase to oxidation in the presence of a diluent and the oxidation reaction products are quenched with aqueous liquid, the steps of returning a part of the aqueous liquid to the quenching zone, continuously removing a part of the aqueous liquid and separating the acids therefrom,

3. Inthe method of producing oxygenated organic compounds wherein aliphatic hydrocarbons are subjected in the vapor phase to oxidation in the presence of steamand th'e oxidation reaction products are quenched with aqueous liquid,

the steps of flashing off from the aqueous liquid al1 products except acids and then reusing the aqueous liquid to quench the oncoming reaction vapors, removing a part of the quench liquid and separating the acids therefrom and adding fresh water.

. part of the remaining aqueous liquid to the quenching zone.

5. In the method of producing oxygenated organic compounds wherein aliphatic hydrocarbons are subjected in the vapor phase to oxidation and the oxidation reaction products are quenched with an aqueous liquid, the steps of flashing off from the aqueous liquid substantially all products except substantially all of the acid present therein, scrubbing the flashed off products with just su'icient water to remove any acid i contained therein, adding this water to the aqueous liquid coming from the flashing step removing a part of such aqueous liquid and separating the acids therefrom, returning at least a part of the remaining aqueous liquid to the quenching zone while introducing fresh water.

JOSEPH E. BLUDWORTH. 

